Simulating lettuce production in a multilayer moving gutter system
For optimal cultivation planning, a model of a double-layer multigutter system (MGS) was designed with lettuce as model crop, and implemented in an existing greenhouse simulator Virtual Greenhouse (VG). The model is based on deterministic equations of lettuce physiology, and validated with data attained from a commercial lettuce producer with single-layer MGS in Slovenia. A comparatory simulation study of regular cultivation (non-MGS) and MGS with single and double layers was done. Simulations were performed for a complete year, taking specific cropping measures into account. Each batch was simulated with set points between 0 and 20 daily light integral (mol light photons m-2 crop area day-1) for the top compartment and the lower compartment separately. Because of lower natural light in the bottom compartment, the realised daily light integral (DLI) was different between the top and bottom when setting DLI between 0 and 20 mol m-2 day-1. Simulations show that the MGS with double layer can strongly improve cultivation output, but thorough planning of the layer positioning moving speed of the gutters needs to be done In addition, large amounts of surplus heat energy from lamps when using high DLI set points needs to be removed. Individual crop yield, i.e., weight of lettuce heads, for cultivation over a year depends on the amount of lighting used, and is higher with regular cultivation or single layer when no or low assimilation light is used in the bottom compartment of a double layer. The two-layer cultivation, however, can double the yield in terms of number of lettuce heads per year and m2 compared with a single-layer MGS cultivation, and 75% higher than in a traditional growing system with fixed plant distances. High energy use for lighting, however, is necessary for high output.
Körner, O.; Pedersen, J.S.; Jægerholm, J. 2018. Simulating lettuce production in a multilayer moving gutter system. Acta Horticulturae 1227, 283-290.